Acoustic alarm device



March 20, 1945. s. A. BJERGEL ACOUSTIC ALARM DEVICE Filed Nbv. 4, 1941 3 Sheets-Sheet 1 -Fi Fig/a 4, I. G ac 4M March 20, 1945. s. A. BJERGEL ACOUSTIC ALARM DEVICE Filed Nov. 4, 1941 5 Sheets-Sheet 2 March 20, 1945. s. A. BJERGEL ACOUSTIC ALARM DEVICE s Sheets-Sheet 3 Filed Nov. 4, 1941 Patented Mar. 20, 1945 mums, v v AGO'US'TIQ Ammunition V r Sven As oBiessc St o m, Sweden; ssigns: to Tele onak i olas th M- i sson 51 holm, w den, a company. Sweden Application November 4, 1941; semi No.'41*l,869 y In Sweden Februawrlhflflfl l y I 6 Claims. (.01. 17:14)

The present invention refers tolan acoustic alarm device. Such alarm devices are known andtheir function is based on :the principle that a diaphragm against which a strong air current or.:a current of some othergaseous .di.-' rected, under certain conditions beglnsto vibrate; thus producing aloud sound. In. order .to obtain the sound in'the alarm device accordingsto the. principle inlquestion itis necessary that the dim ohragm ea ransed at a certain dis ance :imm t e, m u h pi ce f m whi h the airflow and th ta-no ms pro ided, in wh ch ce tain 9.5 11 1%: tlons depen ent on the frequ ncy conditio s m y be p u ed K n acous c a rm devices a e usua ly or 1structe v in s h -manner, that an ai current is directed against the centre o the diaphrasin, passin n to the ,hom. The acoustic alarm device a cordin to this construct n, himve p s t a p oble egards th xesula tion of the dis e e n he mouth o th tube nd th iaphragm, t e de ree 01 fl x b lity of the. diaphra m having fu ther a gre t. influence upon the air p essur requ d- .Itis therefore very dif cult an insome as s impossible t start such n acoustic alarm devicaitthe'said distan is much reat or sma er t an correct. o if th btainable air pressure appma hoslthe limit for the lowest possible pressureio; operating the acoustic alarm device. The tension in the stretched d ap agm be n dependent on the temperature, the pressure necessary for starting the acoustic alarm device will-vary considerably with changes in temperature. 7 I "t1 7 The aim of the invention is to construct an acoustic alarm device with good starting qualities so that at W air pressures, it starts to produce sound, and which also at these pressures attains a maximal emission of soundafter awery short interval. Y

' Through the. device according to theinvention such forces are produced on the oscillating diaphragm when an air current is directed against the same that the distance between the diaphragm and the mouth-piece of the air inlet tube automatically will *be corrected at the same time as the diaphragm is forced-to perforrnthe oscillations desired. v

The invention shall-be described *with""-refer- 'ence to the accompanying drawings, in which five embodiments are shown. Fig: *ljs'hows a vertical section and Fig. la a horizontal 'projec tion of the acoustic alarm device according to the first embodiment. {The Figure ,2,"i3 and"4' showa'second embodiment.

I The Figures 5 and 6' show vertical sectionsof a part of an acoustic a larm device according to another. embodiment of theainwention.

Figures '7 and 8 showventicallsectionalpamtsof an acoustic alarm .zdevice-accoxtdingto the fourth g; and fifth embodiments of the invention;

- Inijlligumesl andtla," l istheihouslng of {the acoustic alarm. device, which at. the bottom is pnovided witiba .device afortheattachmentof the alarm The housing carries a horn Land 10 at theupper end acovLer 3 withothe diaphragm '4. In the housing 1| .thene isi-a channel'ffi tor the incoming air. llhe mouth- .of this channelv at the upper end is fonmedlas airplane ringei-ike .seat at which in the centre is provided with a plug 1.

lb. The upper surfaces of the seat and the 'plug are' located in thesame 'plane; The diaphragm 4 is located between the housing land the cover-'3.

' in a planeabove seat 6. :One hole 8 ls ar ranged at the centre of the diaphragmin iront of thenplug ii, the diameter of the hole beingsmaller than thaktof theplugr At least one other hole =9 is formed nearer-the edge-of: the dia phragm ends into the funnel. The part of the housing against which therim of the diaphragm rests, ismade as a planely ground edge,.-concen trically placed around the seat-t and the plug 1. The cover 3,'-by means of wl-iich the diaphragm is fixed in its 'position, forms a chamber 41] above the diaphragm. This chamber communicates through the hole s withthe supplying channel 5 through the opening :9 with the outlet passa ge H under 'the diaphrag-ma "The passage M opens'into the ho-rn 2. g

' In Figures" .1 and la the outlet passage' l i'sof such shape that the horn 2 is disposed singularly with respect to the inlet-channel 5. while in Figur-es 2 to 4 the hornis in parallel relation to and surrounds the inletohann-el. In all other respects these two horns of the inventionare the same,

When the acoustical-arm device-is togi-ve signa'ls, air is supplied to the supplying channel 5.

Air-thereby will flow out between the diaphragm 4 and the seat 6 through the passage ll and horn 2. Simultaneously the air will flow through the 'hole 8 of the diaphragm into the chamber [6 (see-Fig. 3). The air pressure above ,the diaphragm thereby will increasethus pressing the latteragainst the seat 6. The -plug 1 in the supplying channel -5 now completely covers the hole 8 in the diaphragm. fionsequnt-ly the air will be prevented "from "flowin l gi' the chamber 1'0 and-thus the pressure in the same will decrease, asair is coming out through the hole 9 of thediaphragm. -When the total pressure on the upper side of the diaphragm becomes equal to or less than the total pressure of the air, which isflowing in through the channel on the lower side of the diaphragm, the latter returns to its initial position. Air now will 5 pass into the outlet passage II and the horn 2 again, and the above described working will be repeated. In this way the air flowing out inter mittently into the horn 2 thereby will produce a characteristic sound.

The embodiment of the acoustic alarm device shown in Figures 5 and 6 difiers from the previous embodiments only in that, when the dia- Y phragm is at rest, the openings 9 therein are closed by a ring l2 secured to the cover 3. 'Since the ring l2 covers the openings 9 in the diaphragm, the pressure in the air chamber!!! will increase more rapidly according to this embodiment than according to those first mentioned, where the holes 9 are constantly open so that the air maybe blownnutthrough them. When the alarm device is. to produce sounds, air is blown in through the channel 5, as described, above. Air will then: partlyissue into.the.horn 2 and partly enter into theroom l0 above the diaphragm-i and thus effect an increase of pressure in the said room. Thepressure on the upper side of the diaphragm now presses the same down against the seat 6 thereby uncovering the openings 9 through which air is discharged and I the pressurein the chamber I!) will decrease.

For the rest the operation of this embodiment is analogous to the one described in connection with the first embodiments.

Figure 7 shows another embodiment of the acoustic alarm device.. According to this embodiment the holes 9 which let out the air in the chamber H) are not arranged in the diaphragm itself-but between the chamber and the outer atmosphereas indicated at 16. The eiiect of the alarm device, on thewhole is the same as in the embodiment according to the Fig. 2, but further the advantage is obtained that the air passing through the hole lGl arrangedv between the chamber and the outer atmosphere may 4 easily be, controlled from the outside. ,Asa con-, sequence under certainconditions the diaphragm may also be used asa valvefor closing the air supply to the alarm device, thus dispensing with the valve which otherwise had to be connected with the inlet channel as already has been described in connection with the embodiments shown. If the openin I6 is closed between chamber to and'the outer atmosphereby means of a valve IL the diaphragm will be pressed against the mouthpiece 6 of the supplying channel 5 due to the entrance of air through the opening8 of the diaphragm and thereby the further passage of air is prevented. This effect may further be intensified by replacing the plug 1 0f the embodiment above described by a piston l5 which is removed from the diaphragm at the same time as the hole [6 between the chamber and the outer atmosphere is closed, thereby permitting the air pressure in the supplying channel 5 to continue to act upon the upper surface of the diaphragm in the chamber It. It is advisable to arrange the piston i5 on a valve spindle which also carries the valve i7 provided for' the closing of the hole 16. e

In Figure 8 an embodiment of an acoustic alarm device according to the invention is shown according to which the alarm device is governed by an electric relay l4,the armature I la of which acts upon the valve I3 between the chamber In 75 and the outer atmosphere. When this valve I3 is closed the diaphragm is pressed against the mouth 6 on the supplying channel.

The functioningof the acoustic alarm device according to the embodiment shown in Figures 7 and 8 is the following.

When the acoustic alarm device is connected to a pipe for air pressure the air will pass through the channel 5. Air will then pass into the passage I l and through the hole 8 in the diaphragm A. This will cause an increase of the pressure in "the chamber l0 above the diaphragm. The

valves IB, l1 Figure '7 or I3 Figure'8 respectively are closed on this occasion. The diaphragm is now pressed down against the seat so firmly that the air is prevented from penetrating further between the diaphragm and the seat. On account of the inclination of the diaphragm around the seat a small elevation will be produced inthe centre of the diaphragm right in front of the plug 1, thus forming a small air passage through the hole 8. The object of this feeble air current is to provide for the replacement of the air which through leakage for instance on the periphery of the diaphragm might cause a decrease of pressure-in the chamber I0.

' When the acoustic alarm device shall give signal the valves l6, 11 Figures '7 or 13 Figure 8 is opened. This is efiected' in the embodiment according to the Figure 8 by the electric magnet l4.- When the valve in either Figure 7 or 8 has been opened the air from the chamber I0 begins to flow out through this valve and a decrease of pressure in the chamber 15 is obtained, which enables theair pressure from the channel 5 to lift the diaphragm 4 again. Air from the channel now issues between the diaphragm and the seat into thepassage H and through the hole 8 in the diaphragm into the chamber 10. The pressure in the chamber will now increase, and at this the diaphragm will be pressed down against the'sea't, so that the piston 15 or the plug I covers the hole 8 and the mode of operation described earlierin connection with the Figures 2-4 will be repeated. ,If the valve 16, H or I3 is closed, the air which at every vibration enters through the opening 8 into the diaphragm 4, will remain in the chamber Ill and cause an increase of pressure there. When the pressure in this chamber It! has become sufiicient the diaphragm 4 is pressed down against the seat 6 and is retained in this position.

The air from the channel 5 is again prevented by the diaphragm from passing into the funnel. The sound of the acoustic alarm device has ceased and the diaphragm has closed the opening in the channel 5.

'I claim: Y Y

' 1. An acoustic alarm device comprising a housing-with a cover, an inlet channel for a fluid medium pressure arranged within the housing, an outletpassage surrounding the inlet channel, a vibrating diaphragm having one side normally disposed in closely spaced relation to the mouth of the inlet channel and periodically engageable with said mouth to close communication between saidinlet channel and said outlet passage, an air chamber on the other side of the diaphragm between the diaphragm and the cover of the housing, said diaphragm 'having an aperture normally connecting the air chamber with the channel, and a member in front of the aperture interrupt ing the passage of the fluid from the inlet channel to the air chamber, at the same time when ing connecting the air chamber with the outlet passage and means coacting with said opening for controlling the passage of fluid therethrough.

5. An alarm device as claimed in claim 1 in which said cover is provided with an exhaust opening, a valve member controlling passage through said opening, and an electric relay controlling said valve member. 1

6. An alarm device as claimed in claim 1, in

which the diaphragm is provided with an exhaust opening connecting the air chamber with l the outlet passage, and a valve member carried by said cover and normally closing said opening. SVEN AGNE BJERGEL. 

